1. Field of the Invention
The present invention generally relates to radio communication and, more particularly, is concerned with a system for detecting operation of a radio transmitter and providing an indication alerting the radio operator that the transmitter is unintentionally keyed in an "on" condition.
2. Description of the Prior Art
From airplanes, ships, boats, trucks, automobiles and the like, communication is often necessary by wa of two-way radio. Radio communication is the only means by which important information can be conveyed quickly so that actions whether routine or emergency in nature, based on such information an be carried out. Many users share use of the same frequency channels in carrying on such communication. It is important that these channels be maintained open for use to the maximum extent possible.
Many radio sets employ a microphone having a switch or button which is depressed whenever the operator desires to speak and transmit a message. Release of the button by the operator normally results in return of the button to its initial undepressed position. When the button is in its initial undepressed position, the radio is capable of receiving a message transmitted from a distant radio.
Serious problems can arise should the button become stuck in the depressed or keyed position, or a component fails, whereby the radio transmitter is maintained in its "on" or transmitting condition. First, the frequency channel being relied upon by many users will be unintentionally occupied by the stuck radio transmitter for an extended period of time which, in effect, blocks usage of the channel by anyone else. Second, since the transmitter of the radio is stuck in its transmitting condition, receipt of messages from others to inform the operator of the problem is also prevented.
Consequently, a need exists for means to detect the existence of a stuck button or component failure condition and to alert the radio operator so that appropriate corrective action can be taken promptly.